Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$59.47	11.290%	$66.1842	$66.18	$66.20	$66.20
Purchase #2	$89.29	11.236%	$99.3226	$99.32	$99.30	$99.30
Purchase #3	$51.38	7.373%	$55.1682	$55.17	$55.15	$55.20
Purchase #4	$220.69	10.379%	$243.5954	$243.60	$243.60	$243.60
Purchase #5	$67.53	6.798%	$72.1207	$72.12	$72.10	$72.10
Purchase #6	$49.96	6.614%	$53.2644	$53.26	$53.25	$53.30
Purchase #7	$194.95	9.293%	$213.0667	$213.07	$213.05	$213.10
7 purchase totals =	$733.27		$802.7222	$802.72	$802.65	$802.80